The subject matter of the present invention relates generally to veneer lathe apparatus for peeling wood veneer from rotating logs, and in particular to such lathe apparatus having a powered nose bar roll of large diameter positioned in front of the lathe knife blade for compressing the surface of the log during peeling, and for supplying a portion of the torque to rotate such log. The veneer lathe apparatus of the present invention has been found to be especially useful for peeling logs down to an extremely small core diameter of, for example, 21/2 inches for soft wood such as fir, thereby reducing waste and increasing veneer yield. The large diameter nose bar roll also prevents jam-ups of wood chips at the junction between the nose bar roll and the log, and greatly increases cutting time between lathe knife sharpening for more efficient operation of the lathe apparatus.
Previously it has been proposed in U.S. Pat. No. 3,207,194 of Hedberg et al issud Sept. 21, 1965; U.S. Pat. No. 3,680,613 of Daniels et al issued Aug. 1, 1972 and U.S. Pat. No. 4,335,764 of Schmidt issued June 22, 1982 to provide a veneer lathe apparatus with a powered nose bar roll in engagement with the side of the log adjacent the veneer knife blade for rotating the log and applying pressure to the log during peeling. However, in all of these patents the nose bar roll is of relative small diameter which is much smaller than the minimum log core diameter to which the log can be peeled. Thus, a conventional powered nose bar roll is typically on the order of about 5/8 inch in diameter, so that only a relatively small amount of torque can be applied to the log by the powered nose bar roll. In addition, wood chips and other trash tend to lodge at the junction between the nose bar roll and the log which necessitates periodically disengaging such roll and stopping peeling for cleaning purposes to clear the jam-up, thereby resulting in reduced production and variations in the veneer thickness. In the Hedberg and Daniels patents the nose roll has a smooth surface and is driven from one end by a motor connected through a drive chain to a drive shaft which is rigidly coupled to the nose bar roll by a bearing assembly that limits the amount of power which can be transmitted to the nose bar roll. The torque applied to the log by nose bar roll is greatly increased in the present invention by providing a grooved roll surface on such roll, connecting two separate motor drives to the opposite ends of the nose bar roll and coupling the drive shafts of such motors through flexible plastic couplings to the nose bar roll for more efficient power transfer. In the Daniels et al patent the nose bar roll is adjusted vertically and horizontally with respect to the knife blade by means of a fluid cylinder and motor driven worm shaft to provide a variable veneer thickness control but results in a lathe apparatus of much greater cost and complexity.
The Schmidt patent shows a similar teaching and also provides powered backup rolls for engaging the side of the log at a position remote from the knife blade and powered nose bar roll so that such backup rolls can apply additional torque to the log and prevent deflection of small diameter log cores. The backup rolls are mounted on pivoted support members which are geared together to change the spacing of such backup rolls as the log diameter decreases. In Schmidt, the powered nose bar roller is held in a fixed position on spaced support bearings which are lubricated by water. However, there is nothing to indicate that an oil lubrication means should be provided for bearing sleeves in the bearings and the oil passages connected to a supply of pressurized air for blowing the oil out of such oil passages onto the surface of the nose bar roll for more uniform lubrication and to clean such oil passages in the manner of the present invention.
A veneer lathe apparatus having a powered nose bar roll which is driven by a separate drive roll in contact with such nose bar roll is shown in U.S. Pat. No. 3,421,560 of Springate issued Jan. 14, 1969 and U.S. Pat. No. 3,584,666 of Jensen issued June 15, 1971. However, the nose bar roll of these patents is of extremely small diameter less than the minimum log core diameter, and therefore, can apply very little torque to the log for rotation thereof. Both of these patents use backup rolls separate from the nose bar roll for preventing deflection of the small diameter log core after peeling the log to such a small diameter. The Springate patent uses a cam means for adjusting the backup rolls during peeling to enable the log to be peeled to a minimum core diameter of about 4.0 inches. The Jensen patent detects when wood chips, trash or other obstructions become jammed at the junction between the small diameter nose bar roll and the log and disengages the roll from the log to free the jam. This jam-up problem is avoided by the large diameter nose bar roll of the present invention which causes the wood chips and other obstructions to pass beneath such roll.
As shown in U.S. Pat. No. 4,263,948 of Hasegawa issued Apr. 29, 1981 and U.S. Pat. No. 4,269,243 of Hasegawa issued May 26, 1981, a veneer lathe apparatus has been provided with a powered drive roll adjacent the knife including a plurality of large diameter discs spaced apart and extending through slots in a pressure bar so that sharp teeth on such discs engage the log for applying additional torque to rotate the log. However, these spaced discs have the disadvantage that their teeth mark the veneer and they do not compress the log in the space between discs as is required for uniform high quality veneer. Such lathe apparatus are also subject to jamming of wood chips because of the fixed nose bar segments positioned between the discs. These lathe apparatus are complicated and expensive including cam means for adjusting the drive roll relative to the knife. These problems are avoided in the veneer lathe apparatus of the present invention by causing a powered nose bar roll of large diameter to engage the log along substantially its entire length, connecting both ends of the roll to drive motors and by increasing the friction of such nose bar roll by providing grooves in its outer surface extending longitudinally of the bar axis of the roll axis.